At Goat Island Beach it is easy access into the water off the beach. You will see snapper and other fishes in a natural habitat that has been protected since 1975. In summer, schools of kingfish, kahawai and jack mackerel appear. On the reefs red moki, banded wrasse, spotties, kelpfish and goatfish share the habitat with leatherjackets and blue cod. Blue maomao schools are often mixed with sweep, trevally and parore.

Spiny rock lobster, best known as crayfish, are more common in the marine reserves at Tawharanui and Goat Island than the rest of the coast. Rock pools at Goat Island, Matheson Bay and Tawharanui can be explored at low tide to see crabs, sea shells, small fishes, nudibranchs and shrimps.

During winter New Zealand fur seals often winter over on the outer rocks at Goat Island. Occasionally a leopard seal has appeared on beaches but all seals are wild animals and should not be approached within 5 m.

Dolphins and whales are frequent visitors to the surrounding coast. Bottlenose dolphins often pass close to shore and in recent years have spent hours, some days at Goat Island interacting with snorkellers. Common dolphins are smaller and seen away from the coast where they move in large pods. They often feed where the gannets are diving in large numbers. Pods of orca (killer whales) are also frequent visitors and hunt for rays close to the coast. They are the largest dolphin and are being studied in NZ by Dr Ingrid Visser.

Bryde's whales are the most common whale seen in the Hauraki Gulf and it is believed that they are resident in the area, moving further out of the gulf at times or closer to the coast when there is plankton about. Other whales occasionally seen include humpbacks, southern rights, blues and minkes. To see them you just need to be there at the right time.